Food comes from plants (cereals, pulses, fruits, vegetables, oils) and animals (milk, eggs, meat, fish, honey). Foods contain several components, not just one nutrient. A balanced diet provides energy, protein, essential fats, vitamins, minerals, fibre and water in suitable amounts for a person’s needs.

Carbohydrates are a major energy source; fats provide concentrated energy, essential fatty acids and help absorb vitamins A, D, E and K; proteins supply amino acids for growth, repair, enzymes and many hormones. Vitamins and minerals regulate processes and support structures but do not supply calories. Water supports transport, temperature regulation and excretion.

Macronutrients are required in relatively large amounts: carbohydrates, fats and proteins. Micronutrients are needed in smaller amounts: vitamins and minerals. Dietary fibre supports bowel function; it is not digested like starch.

Vitamin A: night blindness/xerophthalmia. Vitamin B1: beriberi. Niacin/B3: pellagra (dermatitis, diarrhoea, dementia). Vitamin C: scurvy/bleeding gums/poor healing. Vitamin D: rickets in children and osteomalacia in adults. Vitamin K: impaired clotting. Iron: iron-deficiency anaemia. Iodine: goitre and thyroid dysfunction. Calcium/vitamin D inadequacy can impair bone health. B12 deficiency may cause megaloblastic anaemia and neurological problems.

Starch: iodine solution → blue-black. Reducing sugars: Benedict’s reagent with heating → green/yellow/orange/brick-red depending on concentration. Protein: Biuret reagent → violet/lilac. Fat: a lasting translucent grease spot on paper is a simple indicator. Tests are qualitative classroom tests and need proper controls.

Digestion breaks large food molecules into absorbable units. Most nutrient digestion and absorption occurs in the small intestine; bile is made by the liver and stored/concentrated in the gallbladder. Bile emulsifies fat but is not an enzyme. Fibre and water support bowel health. A high-calorie diet can still be deficient in micronutrients.

9–4–4 kcal/g: fat 9, carbohydrate 4, protein 4. ADEK = fat-soluble vitamins. C = collagen/gums/healing. D helps calcium absorption; rickets in children. Iodine = thyroid/goitre. Iron = haemoglobin/anaemia. B1 = beriberi; B3 = pellagra. Xylem/phloem are not nutrition nutrients; do not confuse plant transport with human nutrition.

Use local foods and food labels to classify nutrients; avoid labelling foods as containing only one nutrient. Ask learners to justify claims using evidence. Avoid diagnosing a disease from one symptom alone; deficiency disorders require clinical context. Nutrition requirements vary by age, activity, pregnancy and health.

Cell membrane: selectively permeable boundary. Cytoplasm: site of many reactions. Nucleus: most DNA and gene regulation in eukaryotes. Ribosomes: protein synthesis. Mitochondria: major site of aerobic respiration/ATP generation. Plant cells commonly have cellulose cell walls and a large central vacuole; photosynthetic cells have chloroplasts. Mature human red blood cells are a notable nucleus-free exception.

Cell → tissue → organ → organ system → organism. Epithelial tissue covers and lines; connective tissue supports, binds and transports (blood is connective tissue); muscle tissue contracts; nervous tissue conducts signals. Plant meristems divide; xylem conducts water/minerals and phloem translocates sugars.

Respiration: air reaches alveoli for gas exchange by diffusion. Digestion: small intestine is the main site of nutrient absorption; liver makes bile; gallbladder stores it. Circulation: right heart sends blood to lungs; left heart sends oxygenated blood to body. Kidney nephrons filter blood and adjust water/salts. Nervous system coordinates rapid signals; endocrine system uses hormones.

Photosynthesis occurs in chloroplasts of photosynthetic cells; oxygen released in oxygenic photosynthesis comes from water. Stomata regulate gas exchange and water loss. Transpiration is water-vapour loss from aerial parts. Pollination transfers pollen to a stigma; fertilisation follows. Ovule → seed; ovary → fruit. Vegetative propagation is asexual reproduction.

Mitosis usually makes two genetically similar daughter cells and supports growth/repair. Meiosis reduces chromosome number to form gametes and contributes variation. Fertilisation restores the diploid chromosome number. Genes are DNA sequences; traits often reflect both genes and environment. In a simple Aa × Aa complete-dominance cross, genotype ratio is 1:2:1 and phenotype ratio 3:1.

Bacteria are prokaryotes; fungi, plants, animals and protists are eukaryotes. Yeast fermentation produces CO₂ for bread dough; lactic acid bacteria help make curd; Rhizobium fixes nitrogen in legume root nodules; Plasmodium causes malaria and is transmitted by female Anopheles mosquitoes. Viruses require host cells to replicate. Antibiotics target bacteria, not ordinary viral infections.

Structural adaptation: webbed feet, spines, insulating fur. Behavioural adaptation: migration or nocturnal activity. Physiological adaptation: internal functional changes. Natural selection acts on heritable variation across generations; organisms do not purposefully evolve traits because they need them. Decomposers recycle matter; energy flows through food webs and is lost as heat at each trophic transfer.

Plant cells also have mitochondria and respire day and night. Not every plant cell has chloroplasts. Arteries carry blood away from the heart; veins carry blood toward it (oxygen content is not the rule). Pulmonary artery carries deoxygenated blood; pulmonary veins carry oxygenated blood. Tendon = muscle-to-bone; ligament = bone-to-bone. Neuron = nerve cell; nephron = kidney unit.

Use models, labelled diagrams, microscope observations, safe experiments and evidence-based discussion. A fair test changes one variable while keeping others controlled. Separate observation from inference. For heredity and health topics, use respectful language and avoid implying that every trait is controlled by one gene or that illness is a personal fault.